U.S. patent number 5,963,038 [Application Number 08/870,063] was granted by the patent office on 1999-10-05 for method of testing a connection which includes a conductor in an integrated circuit.
This patent grant is currently assigned to U.S. Philips Corporation. Invention is credited to Franciscus G. M. De Jong, Johannes De Wilde.
United States Patent |
5,963,038 |
De Jong , et al. |
October 5, 1999 |
Method of testing a connection which includes a conductor in an
integrated circuit
Abstract
An integrated circuit includes a sensor which is arranged in the
vicinity of a conductor in the circuit and is capable of measuring
the current through the conductor. This sensor, for example
constructed as a coil, is capable of determining whether a
connection which includes the conductor is in order. It can thus be
tested notably whether the possibly multiple supply connection of
the integrated circuit is appropriately connected to an external
connection terminal.
Inventors: |
De Jong; Franciscus G. M.
(Eindhoven, NL), De Wilde; Johannes (Eindhoven,
NL) |
Assignee: |
U.S. Philips Corporation (New
York, NY)
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Family
ID: |
26142865 |
Appl.
No.: |
08/870,063 |
Filed: |
June 5, 1997 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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795156 |
Feb 7, 1997 |
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Foreign Application Priority Data
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Jun 6, 1996 [EP] |
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96201569 |
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Current U.S.
Class: |
324/537; 324/127;
324/529 |
Current CPC
Class: |
G01R
31/3173 (20130101); G01R 31/2853 (20130101); G01R
15/181 (20130101); G01R 15/202 (20130101); G01R
31/2884 (20130101); G01R 15/205 (20130101) |
Current International
Class: |
G01R
31/3173 (20060101); G01R 31/28 (20060101); G01R
15/20 (20060101); G01R 15/18 (20060101); G01R
15/14 (20060101); G01R 031/02 () |
Field of
Search: |
;324/523,527,529,537,127
;235/492 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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4211548 |
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Oct 1993 |
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DE |
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4430243 |
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Mar 1995 |
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DE |
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Primary Examiner: Do; Diep N.
Attorney, Agent or Firm: Wieghaus; Brian J.
Parent Case Text
This application is a continuation-in-part of Ser. No. 08/795,156
filed Feb. 7, 1997.
Claims
We claim:
1. A method of testing a connection which includes a conductor in
an integrated circuit, the conductor being coupled to an external
connection terminal of the integrated circuit, which method
includes the following steps:
applying a stimulus to the integrated circuit in order to form a
response in the conductor,
detecting a response in the conductor in the integrated
circuit,
characterizing the functioning of the connection on the basis of
the response,
characterized in that the detecting of the response involves the
measurement of current through the conductor by a sensor situated
in the integrated circuit in the vicinity of the conductor.
2. A method as claimed in claim 1, in which the stimulus has a time
dependent behaviour and in which the detecting of the response
involves the measurement of dynamic behaviour of the current
through the conductor by the sensor.
3. A method as claimed in claim 1, in which the sensor comprises a
coil and the measurement of the dynamic current behavior involves
the measurement of an induction voltage in the coil.
4. A method as claimed in claim 2, in which the integrated circuit
includes a circuit coupled to the coil for converting the measured
result into a digital signal.
5. A method as claimed in claim 1, in which the integrated circuit
receives a supply voltage via a supply connection, the conductor
being coupled to the supply connection in order to conduct a supply
current.
6. A method as claimed in claim 5, in which the application of the
stimulus involves a momentary decrease of the supply voltage in
order to cause a variation of the supply current through the
conductor.
7. A method as claimed in claim 5, in which the integrated circuit
includes one or more inputs for receiving patterns, the application
of the stimulus involving the presentation of at least two
predetermined patterns to the inputs in order to cause a variation
of the supply current through the conductor.
8. A method as claimed in claim 1, in which the application of the
stimulus involves the presentation of a test signal of
predetermined frequency to the external connection terminal.
9. A method according to claim 1, wherein a steady state current is
detected by the sensor.
10. An integrated circuit, comprising:
a conductor for conducting a current; and
a sensor arranged within the integrated circuit in the vicinity of
the conductor in order to characterize the current.
11. An integrated circuit as claimed in claim 10, in which the
sensor includes a coil to detect a variation of the current.
12. An integrated circuit as claimed in claim 11, in which the coil
includes two series-connected sub-coils which are situated to
opposite sides of the conductor and have a mutually opposed winding
sense.
13. An integrated circuit as claimed in claim 11, in which the coil
includes at least two layers with windings.
14. An integrated circuit as claimed in claim 11, in which the
conductor is shaped so as to include a bend, the coil being
arranged in an area enclosed by the bend.
15. An integrated circuit as claimed in claim 10, in which the
sensor includes an MR sensor.
16. An integrated circuit as claimed in claim 10, in which the
detection device includes a peak detector which is coupled to the
sensor in order to convert a voltage to be measured in the sensor
into a digital signal.
17. An integrated circuit as claimed in claim 16, which includes a
Boundary Scan Test cell for storing the digital signal.
18. An integrated circuit according to claim 10, wherein the sensor
detects a steady state current in the conductors.
Description
BACKGROUND OF THE INVENTION
The invention relates to a method of testing a connection which
includes a conductor in an integrated circuit, the conductor being
coupled to an external connection terminal of the integrated
circuit, which method includes the following steps:
applying a stimulus to the external connection terminal,
detecting a response in the conductor in the integrated
circuit,
characterizing the functioning of the connection on the basis of
the response.
The invention also relates to an integrated circuit which includes
a conductor for conducting a current and a detection device for
characterizing a current through the conductor.
A method and an integrated circuit of this kind are known from U.S.
Pat. No. 5,068,604 in the name of Applicant. The known integrated
circuit includes a plurality of supply connections, each of which
is connected to a common supply source, the supply connections also
being internally interconnected. The test aims to check whether
each of the supply connections is correctly connected to the supply
source and conducts a relevant part of the supply current to the
internal part of the circuit. To this end, a voltage difference is
measured across some internal points in the conductor and it is
checked whether this voltage difference remains within a given
margin. To this end, the known integrated circuit includes a
comparison circuit for comparing the voltage difference. A problem
encountered while using this test method is the fact that the
voltage difference to be measured is small since the conductor has
a low, process-dependent resistance so that it is difficult to
execute the above test. A further problem consists in that the
complexity of the test increases as there are more supply
connections, each of which is connected to a common supply
source.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a method of the kind
set forth which can be more readily carried out and offers improved
fault detection in comparison with the known method. To this end,
the method in accordance with the invention is characterized in
that the detection involves the measurement of current through the
conductor by means of a sensor situated within the integrated
circuit in the vicinity of the conductor in the integrated circuit.
The measurement of the current through the conductor by the sensor
is a suitable method of determining whether the relevant connection
terminal is externally connected and/or whether the conductor
functions correctly. There is the advantage that in a situation in
which the conductor carries a constant current, this current is not
at all influenced by the sensor. When the integrated circuit
includes several external connection terminals and associated
conductors, these conductors can be tested independently of one
another when each conductor is provided with a respective sensor.
The sensor can be constructed in various ways so as to measure the
field produced by the current through the conductor. Examples in
this respect are a Hall sensor, an MR (magnetoresistive) sensor and
a GMR (giant magnetoresistive) sensor.
In a version of the method according to the invention the stimulus
has a time dependent behaviour and the detecting of the response
involves the measurement of dynamic behaviour of the current
through the conductor by means of the sensor. Such a dynamic test
method allows the detection of smaller signals and provides a more
reliable assessment as to whether the connection and the conductor
function properly. Furthermore, the application of a dynamic
stimulus makes it possible to use a coil as sensor for detecting
the response. The dynamic stimulus causes a change in current
through the conductor, which causes an induction voltage in the
coil near the conductor. This voltage can be detected and used to
assess the connection.
In a version of the method according to the invention the measured
result is converted into a digital signal. The digital signal can
be simply processed in the integrated circuit. For example, when it
has thus been established that a supply connection is not connected
to the supply source, the circuit can enter a mode which requires
less current. The digital signal can also be fed out from the
integrated circuit as an indication of correct or incorrect
functioning of the relevant connection.
In a version of the method according to the invention the
integrated circuit receives a supply voltage via a supply
connection, the conductor being coupled to the supply connection in
order to conduct a supply current. When the method according to the
invention is used for a circuit with multiple supply connections
and associated conductors, it can be determined whether each of the
supply connections is correctly connected to the supply source.
This is important, for example for operation of the integrated
circuit within specifications and also for the service life of the
integrated circuit.
In a version of the method of the invention the application of the
stimulus involves a momentary decrease of the supply voltage in
order to cause a variation of the supply current through the
conductor. Decreasing the supply voltage is a simple way of
realizing a variation of the current through the conductor. This
variation produces a signal in the sensor, for example an induction
voltage in the coil when a coil is used as the sensor; this signal
can be measured and processed.
In a version of the method of the invention the integrated circuit
includes one or more inputs for receiving patterns, the application
of the stimulus involving the presentation of at least two
predetermined patterns to the inputs in order to cause a variation
of the supply current through the conductor. Because the transition
from one pattern to the other pattern causes a variation of the
supply current, a signal can thus be simply generated in the
sensor. A tester can simply present the patterns as part of the
test patterns already present and can record the response thereto,
possibly in digital form.
In a version of the method of the invention the application of the
stimulus involves the presentation of a test signal of
predetermined frequency to the external connection terminal.
Because the sensor, for example the coil and the associated circuit
section, is sensitive to signals of a frequency in a given
frequency band, a test signal having such a frequency can be
presented to the connection terminal whereto the conductor is
coupled, after which it can be measured whether the sensor receives
this signal. The connection can thus also be tested for correct
functioning.
It is a further object of the invention to provide an integrated
circuit of the kind set forth which can be tested more easily than
the known integrated circuit. To achieve this, the integrated
circuit according to the invention is characterized in that the
detection device includes a sensor arranged in the vicinity of the
conductor in order to characterize the current. The
characterization of the current can be used to determine whether an
externally applied stimulus has influence on the conductor. It can
thus be simply detected whether the integrated circuit is connected
to an external connection and whether the relevant connection
functions correctly. It is notably when a plurality of conductors
are to be connected to the same external connection (as is the
case, for example for multiple supply pins) that the invention
enables simple testing whether each of the supply pins is indeed
connected to the external connection.
In an embodiment of the integrated circuit according to the
invention the sensor includes a coil. A coil is an inexpensive
sensor which can be readily implemented in the integrated circuit
so as to measure a variation of the current. The coil can be formed
during the same process steps as the other conductors of the
integrated circuit.
In an embodiment of the integrated circuit according to the
invention the coil includes two series-connected sub-coils which
are situated to opposite sides of the conductor and have a mutually
opposed winding sense. Due to the opposed winding sense of the
sub-coils, the assembled coil is less sensitive to interference
fields external of the conductor because of the common mode
rejection then occurring. Furthermore, the sensitivity of the
composite coil to a field generated by a current variation in the
conductor is thus enhanced. The testing of the connection will thus
be more reliable.
In an embodiment of the integrated circuit according to the
invention the detection device includes a peak detector which is
coupled to the sensor in order to convert a voltage to be measured
in the sensor into a digital signal. The digital signal can be more
readily processed or fed out from the integrated circuit.
An embodiment of the integrated circuit according to the invention
includes a Boundary Scan Test cell for storing the digital signal.
The connection can be easily tested in conformity with the Boundary
Scan Test standard.
These and other aspects of the invention will be apparent from and
elucidated with reference to the embodiments described
hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 shows a part of an integrated circuit according to the
invention,
FIG. 2 shows an alternative embodiment of the coil in the
integrated circuit according to the invention,
FIG. 3 shows an alternative arrangement of the coil in the
integrated circuit according to the invention,
FIG. 4 shows diagrammatically a method of processing the induction
voltage,
FIG. 5 shows an alternative embodiment of the sensor in the
integrated circuit according to the invention, and
FIG. 6 shows an alternative arrangement of the MR sensor in the
integrated circuit according to the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Corresponding reference numerals in the drawing denote
corresponding or similar parts.
FIG. 1 shows a part of an integrated circuit according to the
invention. The integrated circuit 102 includes a conductor 104
which is coupled to a so-called bond pad 106. The integrated
circuit also includes (not shown) an internal section of the
circuit, for example an electronic circuit which has a given
functionality, is connected to the conductor, and is optionally
packed in a package with pins. Signals can be exchanged between the
external environment and the circuit within the package. The bond
pad 106 is connected to such a pin or directly to the external
environment by way of a bond wire 108. The connection of the
integrated circuit to a supply voltage is an example of the
foregoing. The package is then mounted on a printed circuit board
(PCB), the relevant pin then being connected to a supply track for
the supply voltage on the PCB. The complete connection thus formed
includes the following parts: a coupling from the supply track to
the pin of the package, a coupling from the pin to the bond wire
108, a coupling from the bond wire to the bond pad 106, a coupling
from the bond pad 106 to the conductor 104, and finally a coupling
from the conductor 104 to the integrated circuit. The integrated
circuit 102 also includes a coil 110 which is situated adjacent the
conductor 104. Because the coil is situated near the conductor,
inductive coupling exists between the conductor and the coil.
Therefore, a variation of the current through the conductor 104
will cause an induction voltage in the coil 110. This coil thus
enables testing as to whether the described complete connection is
in order. For example, a pulse is then applied to the supply track
of the PCB and it is measured whether the associated induction
voltage arises in the coil 110. A fault in the connection, for
example no contact between the pin of the package and the supply
track on the PCB or a faulty bond wire, can thus be simply
detected.
The described method of testing a connection can be very
advantageously used for an integrated circuit including multiple
supply pins and ground pins. Each supply pin and each ground pin
then has a connection as described above, including: a pin, a bond
wire, a bond pad and a conductor in the integrated circuit. Two
circuits marketed by Philips are examples of such integrated
circuits, i.e. the SAA 4990 video processor IC with 8 supply pins
and 8 ground pins, and the SAA 4991 video processor IC with 7
supply pins and 13 ground pins. Multiple construction of such pins
in circuits of this kind is necessary inter alia in order to
conduct the required comparatively large supply current to
different parts of the integrated circuit via different conductors,
and also to achieve a given quality in respect of signal
processing. All of the multiple supply pins must usually be
connected to the same supply track of the PCB and the multiple
ground pins to the same ground track of the PCB. Should one of the
pins not be connected, the integrated circuit will operate
nevertheless because all parts still receive current via internal
connections, however, the operation of the circuit will not satisfy
all specifications or the service life of the circuit will be
reduced. When a coil is inserted for each conductor coupled to a
supply pin or to a ground pin, each individual connection can be
checked as to whether it is in order. This can be realized by
applying a stimulus to the supply track or to the ground track and
measuring whether the associated induction voltage is generated in
the relevant coils.
When the integrated circuit includes a plurality of conductors
along which a coil is arranged so as to test these conductors, it
is advantageous to make at least parts of adjacent conductors
extend mutually perpendicularly and to arrange the coils adjacent
said mutually perpendicular parts. Adjacent coils are thus arranged
perpendicularly to one another so that the coupling between a
conductor and the coils, if any, of adjacent conductors is
minimized.
The coil 110 can be realized in the integrated circuit by the same
process as used to form the other conductor tracks for the
integrated circuit. In an embodiment of the integrated circuit
according to the invention the coil is composed of a track having a
width of 2 .mu.m and comprises three turns. The length 112 of the
coil amounts to approximately 100 .mu.m and its width 114 to
approximately 35 .mu.m. In an alternative embodiment the coil
comprises nine turns; to this end it is constructed as a stack
comprising three layers of three turns each. The process used to
construct the integrated circuit should then be suitable for
forming multilayer metal layers in the integrated circuit.
The invention is by no means restricted to the foregoing example
concerning the testing of a supply or ground connection of an
integrated circuit. The invention can also be used for a so-called
Multi Chip Module, in which a number of integrated circuits are
combined so as to form one unit. In such an assembly integrated
circuits can also be provided with a coil adjacent a conductor for
a given current, thus enabling testing of the connection. The
invention can also be used for conductors for a current other than
a supply current. In that case the relevant connection can again be
tested by means of a coil arranged adjacent the conductor.
FIG. 2 shows an alternative embodiment of the coil in the
integrated circuit according to the invention. The coil 110 now
comprises two sub-coils 202 and 204 which are arranged to both
sides of the conductor 104. The sub-coils are interconnected via a
track 206 and have a mutually opposed winding sense. An
interference field passing through the sub-coils in the same
direction will induce opposed voltages in the sub-coils, which
voltages attenuate one another. This effect is referred to as
common mode rejection. The coil as a whole, therefore, is less
sensitive to such interference fields than a single coil. A field
generated by a current variation in the conductor extends
circularly around the conductor. As a result, this field passes
through one sub-coil in one direction and through the other
sub-coil in the opposite direction. Because of the opposed winding
sense of the sub-coils, the induction voltages of the sub-coils
intensify one another so that the coil as a whole delivers a higher
voltage. In comparison with a single coil the composite coil shown
in FIG. 2 produces, a higher induction voltage for a given current
variation in the conductor and it is also less sensitive to
interference. As a result, smaller current variations can be
measured and the current variations can also be measured more
reliably.
FIG. 3 shows an alternative arrangement of the coil in the
integrated circuit according to the invention. The conductor 104
extends at a given angle 302 and the coil 110 is situated within
the area enclosed by said angle. When a current variation occurs in
the conductor 104, the field around the conductor portion 304 as
well as the field around the conductor portion 306 will pass
through the coil 110. As a result, an induction voltage arises in
the coil which is higher than if the coil were situated adjacent a
completely straight conductor. The conductor shape shown in FIG. 3
yields a higher inductive coupling between the conductor and the
coil. Furthermore, a second coil can again be used as described
with reference to FIG. 2. This second coil can be arranged in the
area enclosed by the angle 308.
The induction voltage can be processed completely within the
integrated circuit, but can also be fed out from the integrated
circuit as a response signal. An example of complete local
processing consists in that given parts of the circuit are switched
on or off in dependence on whether or not the conductor carries a
current. Feeding out the response signal is suitable as part of the
testing of the fixation of the integrated circuit on a printed
circuit board. A tester then presents given test signals and
receives the response signals from the integrated circuit via an
appropriate output. FIG. 4 shows diagrammatically an example of the
processing of the induction voltage. The induction voltage is then
applied from the coil 110 to an amplifier 402. The output of the
amplifier is connected to a peak detector 404 which checks whether
or not the amplified signal exceeds a given threshold during a
given period. The peak detector produces a digital value which
indicates whether or not the threshold has been exceeded. The
digital value "1" then signifies, for example that the threshold
has been exceeded and the digital value "0" that it has not been
exceeded. The amplifier 402 is known per se and should be suitable
to amplify a signal of the order of 1 mV to an output voltage of
approximately 1 V. A peak detector 404 is also known and is
described, for example in European Patent Application Number
95202835.5/ in U.S. patent application Ser. Nos. 08/734,009
08/734,009 filed Oct. 18, 1996 in the name of Applicant. The value
generated by the peak detector is stored in a register 406 via
which it can be fed out. An example of a register 406 consists of a
Boundary Scan Test (BST) cell which forms part of the BST chain of
the integrated circuit. The BST cell enables testing of the
connection in conformity with the BST standard method. Furthermore,
the connection can then be tested internally and externally of the
integrated circuit in the same way as the other connections. In
this embodiment of the integrated circuit in accordance with the
invention the amplifier and the peak detector are included in the
integrated circuit; however, they could also be constructed so as
to be external of the integrated circuit, for example as part of
the test environment. Furthermore, in order to carry out the
invention the use of a peak detector 404 and a register 406 is
optional and the response on the basis of the induction voltage in
the coil 110 can also be fed out from the integrated circuit in
other ways.
According to the described method a stimulus is applied to the
connection to be tested, said stimulus causing a current variation
in the relevant conductor in the integrated circuit if the
connection is in order. Such a stimulus can be realized in various
ways. For the testing of a connection to a power supply, being a
connection to the supply source as well as a connection to ground,
the stimulus can be applied by momentarily decreasing the supply
voltage. This causes a variation of the current through the
relevant conductor, which variation results in an induction voltage
in the coil adjacent the conductor. When the voltage is decreased
only to such an extent that the peak detector and the register
described with reference to FIG. 4 continue to operate, the
response can be output in the described manner. Another possibility
of applying a stimulus for these connections is to utilize the
phenomenon that the integrated circuit requires a small supply
current in a given state and a large supply current in another
state. An example of a state in which the circuit requires a
comparatively large supply current is a state in which all of the
output buffers output the logic values requiring most current
according to the relevant technology. Depending on the technology
used, this is a logic "1" or a logic "0". Such switching of the
circuit from one state to the other can be realized by means of
BST, because this method enables control of the output buffers of
the circuit. The use of BST is appropriate if the circuit already
includes the BST logic. However, there are also other ways of
controlling the buffers, for example on the basis of functional
signals on the inputs of the circuit yielding an output signal
consisting of logic "1"s. It is to be noted that not the absolute
value of the supply current is relevant but only the difference
between the values of the supply currents in the different states.
Switching the circuit from one state to the other state causes a
variation in the supply current through the relevant conductors,
resulting in an induction voltage in the relevant coils. Checking
whether the associated induction voltage is indeed generated in
each of the coils reveals whether each of the supply connections is
indeed connected. A further method of stimulus application which is
suitable for supply connections as well as for other connections
involves presentation of a test signal of a given frequency. A
given combination of coil and conductor is sensitive to signals in
a given frequency band. The relevant connection can be tested by
applying a test signal having a frequency within said frequency
band to the external track and by checking whether an induction
voltage arises in the coil of the conductor to be tested. A test
signal of this kind can be superposed on the supply voltage, if
any, without damaging the integrated circuit.
FIG. 5 shows an alternative embodiment of the sensor in the
integrated circuit according to the invention. An MR
(magnetoresistive) sensor 502 is situated near conductor 104 in a
layer of the integrated circuit above or beneath the layer in which
the conductor is realised. The MR sensor comprises connection areas
504 and 506 to which through holes 508 and 510 are connected for
measuring the actual resistance of the sensor. An MR sensor has a
resistance that is dependent on an external magnetic field through
the plane of the sensor. Different types of MR sensors exist. The
traditional MR sensor has a layer of anisotropical magnetic
material and current through this layer is influenced by an
external magnetic field, which causes the change in resistance. The
GMR (Giant MagnetoResistive) sensor has a layer of magnetic
material in a fixed direction and a layer of magnetic material of
which the magnetic direction can be influenced by an external
magnetic field, which causes the change in measured resistance.
Depending on the type and construction, an MR sensor is more
sensitive in one direction and less sensitive in another direction
in the plane of the sensor. The MR sensor 502 is constructed in
such a way so as to obtain a large effect from the current through
the conductor on the resistance of the sensor. The current through
the conductor causes a circular magnetic field around the conductor
through the plane of the sensor and perpendicular to the conductor
in the plane of the sensor. The MR sensor 502 is sensitive in this
direction and therefore suitable to measure the strength of the
magnetic field produced by direct current through the conductor.
Based on this strength the value of the direct current can be
determined. So the MR sensor can be used to determine whether the
conductor carries the expected current. This can be used to
determine whether the relevant connection terminal is externally
connected and/or whether the conductor functions correctly. If
multiple MR sensors are used to measure the current through
respective conductors, the MR sensor could be connected to each
other so as to form a bridge arrangement. The current can then be
measured in a more accurate way. According to the invention, a
traditional MR sensor or a GMR (giant magnetoresistive) sensor can
be used. A GMR sensor is more sensitive than an MR sensor and can
more reliably measure the current through the conductor.
Alternative to the static measurements, the MR sensor can be used
to determine any dynamic behaviour of current through the
conductor. When a dynamic stimulus is externally applied, a
corresponding variation in the current through the conductor should
take place if the terminal is properly connected and the conductor
as a whole functions properly. This variation in current causes a
variation in the magnetic field through the MR sensor which can be
detected by this sensor. So the MR sensor can also be applied to
perform a dynamic test.
FIG. 6 shows an alternative arrangement of the MR sensor in the
integrated circuit according to the invention. An MR sensor 602 is
situated near the bond pad 106 to which the bond wire 108 is
connected. The MR sensor 602 has connection areas 604 and 606 that
connect the sensor to respective through holes 608 and 610. The
typical attachment of the bond wire 108 to the bond pad 106 is such
that near the bond pad the bond wire is to a certain degree
perpendicular to the surface of the bond pad. A current through the
bond wire then causes a magnetic field 612 in the plane of the bond
pad and the MR sensor, thus causing a change of the resistance of
the MR sensor which change can be detected. A second MR sensor 614
may be situated at another side of the bond pad and combined with
the MR sensor 602 in order to obtain an arrangement that is more
sensitive to the magnetic field 612 than a single MR sensor. In
FIG. 6, the MR sensors are positioned perpendicular to the magnetic
field 612. However, they may be positioned under a different angle
with the magnetic field if they would be more sensitive in a
different direction.
At a connection layer of the circuit, the through holes e.g.
508-510 and 608-610, are connected to connection tracks connecting
the respective MR sensor to some internal detection circuit or to
external measurement points. The resistance of the MR sensor can
then be measured inside in the integrated circuit with the
detection circuit or outside the integrated circuit with a suitable
measurement arrangement.
* * * * *